Arrangement for uniform electrical sound transmission



June 26, 1928.

ARRANGEMENT FOR UNIFORM ELECTRICAL souun TRANSMISSION HAHNEMANN Filed March 24, 1926 2 Sheets- Sheet 1 June 26, 1928. 1,674,683 I w. HAHNEMANN ARRANGEMENT FOR UNIFORM ELECTRICAL SOUND TRANSMISSION Filed March 24, 1926 2 Sheets-Sheet, 2

xllllm Patented June 1928.

UNITED STATES WALTER HAHNEMANN, OF KITZEBERG,

LORENZ AKTIENGESELLSCHAFT,

NEAR KIEL, GERMANY, ASSIGNOR TO C.

OE IBERLIN-TEMPELHOF, GERMANY.

ARRANGEMENT FOR UNIFORM ELECTRICAL SOUND TRANSMISSION.

Applioation'filed March 24, 1926, Serial No. 97,008, and in Germany March 31, 1925.

The invention deals with the problem of providing a sound apparatus which carries out the transformation of mechanical sound energy from and into electric energy as faithfully as possible within an extraordinary large range of frequencies, that is to say, it is to be so constructed that the differ ent sound oscillations which are present in a large complex (for example, in the transformation of music) are transformed and reproduced perfectly, both as regards the absolute magnitude of the sound oscillations on the one hand and above all with regard to their relative loudness of tone on the other hand.

With a view to solving this problem it has already been proposed to permit different, constructively independent, transmitting or recei ing devices to cooperate with one another, each of them having allotted to it a predetermined range of frequency so that the frequency ranges of the individual, constructively independent, oscillation systems are grouped or located adjacent to one another in any desired arrangement, and so that the whole spectrum of. audible frequencies is continuously covered. At the same time the individual, vibratory systems themselves may be composed of several in dividual oscillatory structures so thatthey constitute coupled systems, whose coupling resonance regions are arranged in a row within the frequency range allotted to the individual oscillators.

It has been found that if loud speaking electrical oscillators of the same type are used in such systems, in spite of having equal efficiency, high and low frequencies are reproduced with difi'erent strengths because the so-called efliciency-constant of these devices is dependent upon the frequency.

According to the invention for the three principal ranges of high, medium and low frequencies, the three different, possible types of apparatus can be used at the same time,

namely, the electrostatic apparatus, the electromagnetic apparatus and the electrodynamic apparatus, the electrostatic apparatus being allotted to the transformation and reproduction of the high frequencies, the electrodynamic apparatus being allotted to the t-ransforn'iation and reproduction of the low frequencies and the electromagnetic apparatus being allotted to the transformation and reproduction of the medium frequencies. The electrostatic apparatus is partlcularly suitable for use with high frequencies, compared with the electromagnetic I and the electrodynamic devices which work wlth iron, because with increasing frequency the dielectric losses increase considerably more gradually than the iron losses. The electrodynamic apparatus on the other hand compared with the electromagnetic is more suitable for lower frequencies than the latter apparatus is, because the efficiency-constant of the electromagnetic apparatus .increases or diminishes with the square of the frequency whilst the efficiency-constant of the electrodynamic apparatus only varies with the first power of the frequency.

A further feature of the invention consists in the dilferent degree of efficiency of the different individual electrical vibrators being balanced by the inverse degree of amplification in connection with the' different types. This feature may be applied in connection with apparatus of different type or with apparatus of the same type.

The efiiciency-constant represents, as is well-known from the work of Hahnemann and Hecht (see particularly Physikalische Zeitschrift 20, 1919, Schallgeber und Schallempfanger, I), a measure for the efiiciency of the apparatus and the formulae for this constant are the following:

For the electromagnetic principle:

K 1 Wm For the electrodynamic principle K l nwm.

ing principles set out in the beginnin are provided with am lifying sets whose ment with electrodynamic oscillators, ll

which also in accordance with the guiding princi les explained before, the degree of ampli cation of the amplifying devices connected therewith increase in the direction of higher frequencies.

In all the figures the reference'numeral 1 indicates a sound horn which is coupled with the resonator 2. An oscillatory diaphragm '3 abuts on the resonator 2. This diaphragm carries in the case of the condenser apparatus the one plate 4 of the pair of condenser plates, in the case of the electroma netic apparatus the armature 5 and in t e case of the electrodynamic apparatus the oscillating current conductor 6. The second condenser plate in the condenser apparatus is indicated by 7, the magnetic structure of the electromagnetic apparatus by 8 and the magnetic structure of the electrodynamic apparatus by 9. For the high frequencies a chain of series condensers and shunt inductances which substantially filters out the low frequencies is connected in front of the apparatus associated therewith. For the low frequencies a chain 11 composed of series choke coils and shunt condensers, which 'substantially shuts out the higher frequencies, is connected in front of the apparatus associated therewith. For the apparatus of the medium range of frequency a mixed chain 12, composed of both series andshunt condensers and choke coils, is provided. V V V, are amplifier units, the degree of amplification of each unit being assumed to be the same.

pick-up and the term sound transmitter as a sound emitter or loud speaker.

I claim 1. A device for sound communication comprising a plurality of individual electrical vibrators; a vibrator of the electrostatic type I for the high frequency range, a vibrator of the electromagnetic type for the medium frequency range, and a vibrator of the elec trodynamic type for the low frequency range 2. A comprising electrical vibrators of different type for different ranges of frequencies; a

vibrator of the electrostatic type for the high frequency range, a vibrator of the elecdevice for sound a communication tromagnetic type for the medium frequency a range, and a vibrator of the electrodynainic type for the low frequency range; and a high frequency pass filter circuit connected to the electrostatic vibrator, a medium frequency pass filter circuit connected to the electromagnetic vibrator, and a low frequency pass filter circuit connected to the electrodynamic vibrator.

3. A device for sound communication comprising a plurality of electrical vibrators for the different ranges of frequencies, and amplifiers of different degree of amplification connected to the individual vibrators in the inverse ratio of the efliciency of production of sound of the individual vibrators.

In testimony whereof I aflix my signature.

WALTER HAHNEMANN. 

